A mechanism in which the objective lens moves vertically along the Z-axis is frequently used as the focusing mechanism in conventional optical measuring instruments and optical microscopes.
The structure of conventional microscopes is described briefly referring to the drawings. FIG. 4 is a side view of the principal part of a microscope and FIG. 5 is a plan view of it. In the drawings, (101) is a stand, (102) is a support mounted on the stand (101) for free vertical movement, (103) is a revolver for the objective lens mounted on the support, and (104) is the objective lens mounted on the revolver. At the support (102), a V-groove (105) for a vertical straight movement guide mechanism is formed on both sides as shown in FIG. 5, and opposite to this groove, a V-groove (106) for a vertical straight movement guide mechanism is formed on the stand (101), and a roller or a ball (107) is held between these two grooves. Also, a rack (108) is mounted on the support (102), a shaft (110) with a pinion (109) engaging this rack (108) protrudes from the stand, and an operation handle that is not shown is mounted on this protruded portion. When this operation handle is rotated, the pinion (109) is rotated through the shaft (110), the rack (108) mounted on the support (102) moves vertically, and also the support (102) moves vertically at the same time, allowing the objective lens (104) mounted on the revolver (103) to be focused.
In the conventional microscopes described above, however, since one end of the one side support type support (102) that is asymmetrical with respect to the center of the optical axis is moved vertically for fine adjustment by means of the rack-and-pinion mechanism, the vertical fine movement mechanism is remarkably asymmetrical and the operation is unstable. Variations in environmental temperature, in particular, cause fluctuations of the center of the optical axis, resulting in the unstable image. Since drift due to temperature changes occurs in such a vertical fine movement mechanism, this mechanism cannot be currently used for molecular position measurement or molecular motion measurement.
This invention is therefore intended to solve the above problem by realizing an optical microscope of high stability in which the image of the viewed sample does not become out of focus during observation and no movement (drift) of the object point (object) occurs.